1. Field of the Invention
The present invention relates to an image processing apparatus, a control method of the image processing apparatus, and a computer-readable storage medium for performing motion image processing for converting a frame rate and, more particularly, for performing conversion processing to a higher frame rate, e.g., conversion of an image at 60 Hz into that at 120 Hz.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2006-184896 discusses, as a conventional technique for suppressing motion blur or flicker that occurs when displaying a video image on a display device, a video display method for creating sub-frames with different frequency components from image data and alternately displaying the sub-frames at double speed. With the video display method, high frequency emphasis image data in which a high frequency component is emphasized and low frequency image data having a low frequency component, from which the high frequency component is suppressed is generated from the input image data, and the resultant image data is alternately displayed at double speed. With the technique, the flicker can be suppressed and the motion blur can also be reduced.
A sub-frame is displayed by increasing a drive frequency, like double-speed driving. Then, although the flickers are reduced, high-quality impression or high realistic sensation of a video image may be lost in some cases. The impression that video image quality is high means image quality with high picturesqueness with which gloss, color reproduction, and a sense of depth of an image, and gloss of an object and season (temperature and humidity) are sensed from a screen.
In double-speed driving for displaying two sub-frames, a ratio (distribution ratio of luminance) of a waveform strength of the two sub-frames is set within a range of 1.0:0.0 to 0.5:0.5. Therefore, when the distribution ratio is 1.0:0.0, i.e., when the distribution ratio is small, although the flickers are generated, an image with the high-quality impression is reproduced. When the distribution ratio is 0.5:0.5, i.e., when the distribution ratio is larger, although the flickers are reduced, the high-quality impression is lost.
On the other hand, Japanese Patent Application Laid-Open No. 2002-023707 or Japanese Patent Application Laid-Open No. 2002-70838 discusses that a predetermined luminance difference is provided between two sub-frames. However, depending on an average luminance value of an input frame, the flickers are consequently distinguished, and both the reduction in flickers and the image reproduction with high-quality impression are not established together.